delta copies

Robert Fitzpatrick lists at
Sun Sep 23 03:49:28 GMT 2007

On Sat, 2007-09-22 at 20:00 -0400, Matt McCutchen wrote:
> On 9/22/07, Robert Fitzpatrick <lists at> wrote:
> Delta transfers reduce network traffic between the sending and
> receiving rsync processes at the cost of some extra CPU time and disk
> I/O (e.g., the receiver has to read the old destination file).  The
> reduction in network traffic is only relevant if the two processes are
> on different machines.  When they are on the same machine as in your
> example, there is no point in doing delta transfers, so by default
> rsync does not do them.  You can force rsync to do delta transfers by
> passing --no-whole-file, but I can't imagine why you would want to do
> this unless you are testing to see how much traffic reduction delta
> transfers would achieve.

Yes, of course, I want to use this doing remote transfers. But since I
was not able to get it to work with our remote transfers, I was trying
to do it locally to speed up testing. Are you saying that rsync knows
the difference and will enable/disable delta transfers depending on
whether local or not? However, again, I get the same result doing remote
transfers. Thanks for the tip, I will try some more testing tomorrow
using the --no-whole-file option...


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